The present disclosure generally relates to a cathode material suitable for use in non-aqueous electrochemical cells that comprise copper manganese vanadium oxide and, optionally, fluorinated carbon. The present disclosure additionally relates to non-aqueous electrochemical cells comprising such a cathode material and to such a non-aqueous electrochemical cell that additionally comprises a lithium anode.
Lithium electrochemical cells, which are more commonly referred to as batteries, are widely used in a variety of military and consumer products. Many of these products use high energy and high power batteries. Due in part to the miniaturization of portable electronic devices, it is desirable to develop even smaller lithium batteries with increased power capabilities and service life. One way to develop smaller batteries with increased power capabilities is to develop higher energy cathode materials.
One example of a high energy cathode material is fluorinated carbon (i.e., CFx). CFx is often used with a lithium anode in non-rechargeable (primary) batteries for, among other things, military devices and implantable medical devices. CFx (where x=1.0) has a specific energy of about 860 mAh/g. Other examples of high energy cathode materials include silver vanadium oxide and manganese dioxide, which have specific energies of about 315 and 308 mAh/g, respectively.
The cathodes for rechargeable (secondary) batteries, such as Li ion batteries, generally have lower energy storage capabilities than primary battery cathodes. However, secondary batteries can typically be recharged several hundred times, which significantly reduces the lifetime cost as well as battery disposal costs. Examples of secondary battery cathodes used in Li ion batteries include lithium cobalt oxide, lithium iron phosphate, and lithium nickel cobalt oxide.
To satisfy the demands for longer lasting and/or smaller batteries, there continues to be a need for cathodes exhibiting higher energy, like primary batteries, with partial or full recharging capabilities, like secondary batteries, thus extending the battery's lifetime and effectively reducing the overall cost. Mixed cathode materials have been proposed as one possible approach for achieving such improved primary and/or secondary batteries. Other benefits of mixed cathode materials include enhancing the rate capability and/or stability of the cathode, while maintaining the energy density per unit weight and/or per unit volume. Approaches for achieving such benefits have typically involved mixing a high rate-capable cathode material with a high energy-density cathode material.
U.S. Pat. No. 7,476,467 discloses a cathode material for secondary lithium batteries. The cathode active material comprises a mixture of (A) a lithium manganese-metal composite oxide having a spinel structure and (B) a lithium nickel-manganese-cobalt composite oxide having a layered structure. The cathode active material is said to have superior safety and a long-term service life at both room temperature and high temperatures, due to improved properties of lithium and the metal oxide.
It is known to those skilled in the art that composite cathodes comprising fluorinated carbon with some metal oxide are used for the purpose of providing a battery with reduced voltage delay, improved rate capability, and low temperature performance. For example, U.S. Pat. No. 5,667,916 describes a battery having a cathode mixture of CFx and other materials including, for example, copper oxide, or mixtures of other materials. Similarly, U.S. Pat. No. 5,180,642 discloses electrochemical cells or batteries having a cathode mixture comprising manganese dioxide (MnO2), carbon monofluoride (CFx, where x=1), or mixtures of the two, and other additives selected from the group consisting of vanadium oxide, silver vanadate, bismuth fluoride, and titanium sulfide.
Copper vanadium oxide electrodes are well known in general for lithium batteries. For example, U.S. Pat. No. 4,310,609 discloses using an electrochemical cell having, as a positive electrode, a composite oxide matrix consisting of vanadium oxide chemically reacted with a group IB, IIB, IIIB, IVB, VB, VIB, VIIB, or VIIIB metal, such as copper oxide. U.S. Pat. No. 5,670,276 describes a non-aqueous electrochemical cell having a cathode of copper silver vanadium oxide, which is made from vanadium oxide combined with copper nitrate and silver oxide, or copper oxide and silver nitrate.
Although the energy density of the electrode materials described in both U.S. Pat. Nos. 4,310,609 and 5,670,276 is improved over some active materials, such as manganese oxide, there is still a great need to enhance the electrochemical proprieties and service life of copper-vanadium oxide based electrodes for lithium cells and batteries, particularly for use in combination with high energy density materials such as CFx. We have now discovered that by using a simple and environmentally friendly chemical synthesis, manganese, copper, and vanadium may be combined to form a mixed oxide electrode with increased capacity and a desired discharge profile.